Bolts are sometimes the only suitable option for clamping small size rotors having low bore radii. The head of the bolt is on one side of the bore, the shank of the bolt extends inside the bore, and the threaded portion extends out the other side of the bore, to which a nut is secured in a “thru bolt” configuration. Thru bolts can provide satisfactory access for torquing/untorquing. Bolt weight, nut weight, tightening torques, distance between the bolt's axis and the rotation axis, and rotation speed can be high, which can result in significantly high stresses in the bolt which can limit the bolt life. Lightweight alloys for the bolt have been used to achieve acceptable low-cycle fatigue (LCF) life for the discs, but there are limits in the advantages gainable solely by alloy selection since some properties or features of lightweight materials are typically traded off for their lighter weight.
Accordingly, there remains room for improvement in addressing LCF life of bolts, especially in the context of high stress rotary environments.